Toner blends containing crystalline or semi-crystalline polyester resins with an amorphous resin have been recently shown to provide desirable low melt fusing (also including ultra low melt or ULM), which is important for high speed printing, lower fuser power consumption or both. Toners containing crystalline polyesters are suitable for both emulsion aggregation (EA) toners and conventional jetted toners.
Fluorescent inks, dyes and toners may be used as an authenticating feature in the document security industry. Secure documents, for example, documents that are difficult to forge, may be conventionally created using inks that include fluorescent agents either alone or in combination with ordinary inks and/or pigments. Features printed using fluorescent inks are usually invisible under visible light due to the colorless nature of the security inks or due to masking by other colorants in the document. Under proper illumination, the fluorescent features of the document are revealed in the form of a bright emission by the fluorescent dyes in the visible spectrum. For example, certain bank notes utilize visible features, such as holographic patches, microprinting and microtextures to conceal additional fluorescent threads and/or multicolored emblems embedded in the bank note, which are only revealed under specific light frequencies. Those features provide an increased level of security and authenticity against counterfeiters by making the copying of such a document more difficult.
Although fluorescent inks are available as described above, the use of toners for printing security features is somewhat limited. For example, U.S. Pat. No. 5,554,480, the disclosure of which is hereby incorporated by reference in entirety, describes the use of ordinary organic fluorescent dyes which are applied via non-electrophotographic methods (flexo printing, inkjet and the like). Furthermore, available fluorescent toners may appear colored under visible light, which defeats usefulness as a hidden or invisible security feature.
Improved methods for producing toners which are suitable for use in security documents remain desirable.